Quality assurance program for prototype stereotactic system developed for Neptun 10 PC linac

A prototype stereotactic radiosurgery set was designed and constructed for a Neptun 10 PC linac that is currently being used at Imam Reza hospital in Mashhad. A complete quality assurance program was designed and performed for the constructed system including isocentric accuracy test, localization accuracy test, dose delivery accuracy test and leakage radiation test. Target simulator, control alignment device and plexiglass phantom which were parts of the developed hardware were used to fulfill quality assurance program. The average isocentric shift resulted from the gantry rotation and couch turning were respectively obtained to be 1.4 and 2 mm. The average localization error in the three coordinates was found to be 2.2 mm. The total treatment uncertainty due to all of the probable errors in the system was equal to 4.32 mm. The dose delivery accuracy test was carried out, the result indicated a 3-7% difference between the given and measured dose. The quality assurance tests showed consistent performance of the constructed system within the accepted limits; however, some inconsistency might exist in certain cases. The safety of SRS method is increased when the overall uncertainty is minimized and the treatment of the lesions adjacent to critical organs is avoided

[Assessment of noise level and frequency analysis of equipments used in dental clinics at Mashhad School of Dentistry]

Instruments and equipments used in dentistry field produce sounds with wide spectrum, so dentists and other personnel are exposed to these sounds continuously. The purpose of this study was measuring the received noise level of personnel working in clinics of Mashhad dental school and frequency analysis of sounds at 20-20000 Hz frequency range. In this study, the noise level in operational dentistry, endodontics, prosthodontics, oral surgery, periodontics, pediatric dentistry and orthodontics of Mashhad dental school were assessed in 2004. Sound level measuring device and their establishment and set up were selected in which according to acquired data, the received noise level of dentist and average received noise level of personnel could be calculated. Equivalent noise level [L[Aeq]] measured surrounding central unit of each clinic, was less than 73.2 dB and noise level inside each clinic was less than 69.9dB. The dentists received noise level during work and presence at the studied clinics was measured to be 67.2-83.7 dB. The equivalent maximum noise level in all clinics was related to frequency band of 630 Hz and sounds of operational dentistry, endodontics and periodontics clinics had strong components in high frequency. According to permitted exposure noise level, the received noise level of dentists and personnel in studied clinics were not hazardous, but because of high frequency sounds, it is suggested to repeat the study with systems which can assess analysis of higher frequencies